The 51-year-old actor has retold his incredible childhood tale in the new film 'Farming' - which tells the story of how he was fostered by his Nigerian parents into a white working-class family in Tilbury, Essex where he faced extreme racism.

He told Deadline: ''The writing became a cathartic process to a degree. But I think probably the most challenging part of the whole process was the filming of it. You know, allowing other people to breathe life into your words.

''More importantly, having to relive that experience every single time, over and over again. That was excruciating.

''But I didn't have the luxury of indulging in those feelings. I had to run the show and really get on with it. But that was a very, very challenging part of the process.''

Set in the 1970s and 80s the lead character - played by Damson Idris - is inducted into a white supremacist gang, after being brainwashed into believing their dogma.

The main character later has a life-changing epiphany after trying to commit suicide, and goes on to receive a law degree, eventually entering into acting.

The 'Suicide Squad' actor admits that he has wanted to tell his story for a long time, and began writing as a way to get to sleep at night.

In an interview with Deadline, he said: In total, probably about 16 years. It really started when I literally could not sleep at night, and in order to get some sleep I would write five or 10 pages, and then I would sleep.

''After two weeks, I had about 500 pages of manuscript, and it was my current partner and friend who used to read it before going to work. And he just said to me, ''This is really good.''